On the same error screen press SHIFT+F10 and it will open up a black Window. (a command prompt window)
In the black windows type the word "regedit" (without the inverted commas and hit enter. That will open the registry editor.In the Registry Editor..Browse to....HKLocal machine/SYSTEM/SETUP/STATUS/ChildCompletion, and after highliting childcompletion,on the right hand side check for setup.exe. if the value is 1 change it to 3 (by double clicking on setup.exe and changing the value shown in the box).
Then close the registry editor and then also close the black window.
Then click on OK for the error and the computer will restart and the installation may complete.